code: def test_multidimensional_inputs(self):
      # test taken from issue #835
      # ensures multidimensional input results in a positive definite kernel matrix, with additional jitter
      x = torch.randn(1000, 2)
      kernel = PeriodicKernel()
      with torch.no_grad():
          K = kernel(x, x).to_dense() + 1e-4 * torch.eye(len(x))
          eig = torch.linalg.eigvalsh(K)
          self.assertTrue((eig > 0.0).all().item())
  
file_path: gpytorch/test/kernels/test_periodic_kernel.py
imports: import math
  import unittest
  import torch
  from gpytorch.kernels import PeriodicKernel
  from gpytorch.priors import NormalPrior
  from gpytorch.test.base_kernel_test_case import BaseKernelTestCase
label_desc: Use image node_id 5 for calling the TestPeriodicKernel obj's underlying member method code with example usage: obj.test_multidimensional_inputs() without return types